LONG-TERM FOLLOW-UP OF TREATMENT OF THYROTOXICOSIS BY 3 DIFFERENT METHODS

In view of continuing debate regarding the best definitive therapy for thyrotoxicosis, we examined the long-term outcome of radioiodine (I-131) or surgical treatment of 1918 thyrotoxic patients divided into three groups: those given I-131 at a dose calculated from thyroid size, I-131 uptake and effective half-life to administer a fixed radioactivity dose to the thyroid; those treated with a dose of I-131 (110, 185 or 370 MBq) chosen empirically; and those treated by partial thyroidectomy. A minimum 10-year follow-up was achieved for 1119 patients treated with a calculated I-131 dose; a single dose resulted in control of disease in 90.5%. At 5 years, 18% were hypothyroid, the prevalence rising to 42% at 20 years. Of 504 patients treated with an empirical I-131 dose and followed for at least 5 years, thyrotoxicosis was controlled by a single dose in 89.7%. The rate of hypothyroidism at 5 years (38.5%) was higher than that found in the calculated dose group. A minimum 10-year follow-up was achieved for 295 surgically treated patients; thyrotoxicosis was controlled in 89.2%. The prevalence of hypothyroidism (2% at 5 years, 27.5% at 20 years) was lower than that found after I-131, whether given by calculated or empirical dose. Each of the treatments employed resulted in an acceptable rate of cure of thyrotoxicosis. If maintenance of euthyroidism is the major objective, our findings suggest that surgery represents the treatment of choice. Furthermore, calculated dose I-131 administration has advantages in terms of risk of hypothyroidism over empirical dose treatment. In choosing treatment, these apparent advantages of partial thyroidectomy and calculated I-131 doses over empirical doses of I-131 must be weighed against surgical morbidity, cost and patient inconvenience.